Urethane containing lubricant



United States Patent This invention relates to a synthetic lubricant composition containing a urethane as antioxidant additive. The lubricant composition of the invention comprises an ester type lubricating oil, an antioxidant of urethane selected from the group consisting of where R is a saturated aliphtic hydrocarbon radical, y is an integer from 1 to 8 equalling the valence of the R radical, R is a monovalent hydrocarbon radical and X is oxygen or sulfur.

The above described monoand polyurethanes are advantageously present in the lubricating composition in a concentration between 0.1% and 5%, preferably between about 0.5% and 1.0%, of the lubricant composition. The novel lubricants of this invention are particularly effective in high temperature service with the urethane additive therein exhibiting excellent anti-oxidant properties at severe high temperatures.

The esters which constitute the major portion of the lubricant composition of this invention are broadly de scribed as esters of hydrocarbyl carboxylic acids. They are high molecular weight materials of lubricating oil characteristics derived from alcohols which are usually aliphatic alcohols containing from 1 to 4 or more hydroxyl radicals, and carboxylic acids which are usually aliphatic oarboxylic acids containing from 1 to 4 or more carboxylic acid radicals.

Widely used synthetic ester lubricants are aliphatic esters of saturated aliphatic monoand dicarboxylic acids containing 6-12 carbon atoms. From the standpoint of cost and availability, the preferred carboxylic acids are caproic, heptoic, caprylic, nonylic, adipic, sebacic and azelaic. The monohydric and polyllydric aliphatic alcohols used to form the esters usually contain at least 4 carbon atoms and up to 20 or more carbon atoms. C to C saturated aliphatic alcohols are commonly used such as Z-ethyl hexanol and 2,2-diethyl-1,3-propanediol. Ether alcohols such as Cellosolve and Carbitol may also be used in the formation of the aliphatic diesters of organic dicarboxylic acids used as the lubricating base in compositions of this invention. Alcohols containing two or more hydroxyl radicals and no hydrogen substituted on the beta carbon atom such as trimethylolpropane and pentaerythritol have proven particularly effective in formulating stable high temperature ester lubricants.

Examples of alkyl esters of aliphtic carboxylic acids are the following: di-isoctyl azelate, di-Z-ethylhexyl sebacat-e, di-Z-ethylhexyl azelate, di-Z-ethylhexyl adipatc, dilauryl azelate, di-sec-amyl sebacate, di-Z-ethylhexyl alkenyl-succinate, di-2-ethoxyethyl sebacate, di-2-(2'-methoxyethoxy) ethyl sebacate, di-2-(2-ethylbutoxy) ethyl sebacate, di-Z-butoxyethyl azelate, di-2-(2'-butoxyethoxy) ethyl alkenyl-succinate, pentaerythritol tetracaproate, trimethylolpropane tri-isooctanoate and nonyl caprate.

In addition to such esters, polyester lubricants formed by a reaction of an aliphatic dicarboxylic acid, a dihydroxy compound and a monofunotional compound, which is either an aliphatic monohydroxy alcohol or an aliphatic monocarboxylic acid, in specified mol ratios are also employed as the synthetic lubricating base in the composition of this invention; polyesters of thi type are described in US. 2,628,974 on Polyester Synthetic Lubricants, which issued to R. T. Sanderson on February 17, 1953. Polyesters formed by the reaction of a mixture containing specified amounts of 2-ethyl-l,3-hexanediol, sebacic acid, and Z-ethylhexanol and by reaction of a mixture containing adipic acid, diethylene glycol and Z-ethylhexanoic acid illustrate this class of synthetic polyester lubricating bases.

The sulfur analogs of the above-described esters are also used in the formulation of the lubricating composition of this invention. Dithioesters are exemplified by di-Z-othylhexyl thiosebacate, di-n-octyl thioadipate and the dilaurate of 1,5-pentanedithiol; sulfur analogs of polyesters are examplified by the reaction product of adipic acid, thio glycol and Z-ethylhexyl mercaptan.

As heretofore stated the anti-oxidant additive ingredient of the novel composition is a urethane of the formula PR is a saturated mono or polyvalent aliphtic hydrocarbon radial of from 3 to 20 carbon atoms such as our,

C52H5 OH2 oinoHid-oHi-, oH,-( 3(cH;) -d1i-CH 117- E R is a monovalent hydrocarbon radical of l to 40 carbon atoms such as the alkyl, aryl, alkaryl and aralkyl radicals, e.g., phenyl, naphthyl, to lyl, xylyl, phenylpropyl, hexyl, isooctyl, decyl and nonadecyl.

Specific examples of the urethane additives contemplated herein are triphenylurethane of trimethylolpropane, LS-diphcnylurethane of 2,2 dicthyl-l,3-propanediol, triphenylthiourethane of trimethylolpropane, 1,3-diphenylthlourethane of 2,2- diethyl-1,3-propanediol and l-hexylurethane of l-isooctanol. These urcthanes are normally prepared by reacting aliphatic alcohol with isocyanate or thioisocyanate at an elevated temperature e.g. between about and 250 F. for a period of several hours. The reaction is usually conducted in the liquid phase, therefore, suitable inert liquid solvent such as benzene, toluene, heptane, propylether or triethylamine is employed when necessary. As heretofore stated advantageously between 0.1 and 5.0%, preferably between about 0.5 and 1.0% urethane additive is present in the novel composition. Additive concentrations above the maximum advantageous range value although providing some additional antioxidant protection do not warrent the increase amounts since this additional increase in protection is small in relation to the amounts employed. The reason for this is that the urethanes are normally insoluble in the synthetic ester base at percentages above about 5.0%. At concen trations below the minimum level of the advantageous range the anti-oxidant effect of the urethanes is not significant.

In a preferred embodiment of the novel composition phenothiazine is used in conjunction with the urethane additives contemplated herein in amounts between 0.2 to 1.5% of the lubricant with concentrations between 0.5 and 1.3% normally being employed. Phenothiazine is very widely used as an anti-oxidant in ester base lubricant. The combination of phenothiazine and a urethane as contemplated herein have been found to be a very satisfactory anti-oxidant combination, the combination having synergistic like anti-oxidant properties in many instances.

The finished lubricant compositions containing the urethane additive or the combination of a urethane and phenothiazine may also contain other well known additives such as viscosity index improvers and extreme pressure agents.

The effectiveness of the anti-oxidant additive contemplated by the invention was demonstrated in a modification of the oxidation test of MIL-L-7808B designed to evaluate lubricants at severe high temperature operating conditions. The modification involved the running of the oxidation test at 500 F. for 48 hours rather than at the usual conditions of 347 F. for 72 hours.

The following lubricant compositions were tested in the modified oxidation test, the results of which are reported in subsequent Tables I, II and III.

(1) Table I:

(a) Lubricant A-100% di-2-ethy1hexy1 sebacate.

(b) Lubricant B-99% di-Z-ethyl sebacate and 1% triphenylurethane of trimethylolpropane.

(c) Lubricant C-99% di-2-ethylhexyl sebacate and 1% phenothiazine.

(d) Lubricant D-98% di-2'ethylhexyl sebacate, 1% triphenylurethane of trimethylolpropane and 1% phenothiazine.

(e) Lubricant E--98.5% di-2-ethylhexyl sebacate, 0.5% triphenylthiourethane of trirncthylolpro-pane and 1% phenothiazine.

(f) Lubricant F-98.5% di-Z-ethylhexyl scbacate, 1% phenothiazine and 0.5 diphenylurethane of 2,2 diethyl-1,3-propanediol.

(2) Table H:

(g) Lubricant G-100% Ester T (tetraester of pentaerythritol and a mixture of nacaproic, n-heptoic, n-caprylic and n-nonylic acids).

(11) Lubricant H-99% Ester T and 1% phenothiazine.

(i) Lubricant I-99% Ester T, 0.5% triphenylurethane of trimethylolpropanoi and 0.5% of phenolthiazine.

(j) Lubricant ]-9'8.5% Ester T, 0.5% triphenylurethane of trimethylolpropane and 1% of phenothiazine.

(k) Lubricant K98.5% Ester T, 0.5% triphenylthiourethane of trimethylolpropane and 1% phenothiamine.

(3) Tablelll:

(l) Lubricant L--100% of trioctanate of trimethylolpropane.

(m) Lubricant M-99% trioctarrate of trimethylolpropane and 1% phenothliazine.

(n) Lubricant N99% trioctanate of trimethylolpropane and 1% of triphenyilurethane of trimethylolpro-pane.

(o) Lubricant O-99% trioctanate of trimethylolpropane, 0.5% triphenylurethane of trimethylolpropane and 0.5% of phenothiazine.

The test data gained from the employment of the above compositions in the modified oxidation test are reported in following Tables I-III:

TABLE I Anti-Oxidant Action of Polyurethanes and Phcnothiazine in Di-Z-Ethylhexyl Sebacatc Lubricant Comp A B C Anti-oxidant wt. percent:

Polyurethane Phcnothiazine Properties of Unused Lube Comp.:

Kin. Vise. (es) C hm o DIG} Oovon Vise.

210 F Appearance of Oil, Wt.

Percent Sludge 100 I Cs.=eentistokes. 1 Unmeasurable-lube oxidized to sludge.

4 TABLE II The Anti-oxidant Action of Polyurethancs and Phenothiazinc in Tetraestcrs 0f Pentaerytlzritol and Mixture of C -C n-Monobnsic Fatty Acids Lubricant Comp G 11 I J K Antioxidant Wt. percent:

Polyurethane 0 0 0. 5 0. 5 0. 5 Pllcnothiazine 0 1 0. 5 1 1 Properties of Unused Lube Comp;

Kin. Vise. (es.)

Sludge 0 0 0 O 0 Oxidation 'lest 500 i i/48 hrs: Used Lube Comp. l)otn- Percent Kin. Vise. Change:

100 F 560 130 115. 0 210 F 290 55 80.0 Appearance 0i cent Sludge 40 0 0 0 (l I Cs.=centistokes. 2 Unmeasurable-lubc oxidized to sludge.

TABLE III The Anti-Oxidant Action of Polyurethanes and Phenothiazine in the Trioctanate of Trimethylolpropane Lubricant Comp L M i N 1 O Antioxident wt. percent:

Polyurethane 0 0 1 0. 5 Plienothiazine 0 1 0 0.5 Properties of Unused Lube Comp:

Kiu. Vise. (cs) F 17. 9 18.1 18 18.9 210 F 3.9 4.0 4.0 4.1 Appearance of Oil, Wt. percent S]u lgc D 0 0 0 Oxidation Test 500 FMS hrs: Used Lube Comp. Date- Percent Kin. Vise. Change:

100 F 360 r 50 0 F 210 35 Appcarance Oi Oi percent Sludge. 50 0 0 0 1 Os-centlstokcs. 'A immeasurable-lube oxidized to sludge.

The data in the above tables clearly demonstrate the anti-oxidant action of the urethanes contemplated herein and the combination of the urethanes and phenothiazine.

All percentages heretofore and hereafter recited are based on weight unless otherwise stated.

We claim:

1. A lubricant composition comprising as the major component an ester formed from an acid selected from the group consisting of saturated aliphatic monocarboxylic acid and saturated aliphatic dicarboxylic acid of 6 to 12 carbon atoms and a saturated aliphatic alcohol of 6 to 18 carbon atoms containing 1 to 4 hydroxyl groups and as a minor component between 0.1 to 5.0 wt. percent of a urethane of the formula wherein R is a saturated aliphatic hydrocarbon radical of from 3 to 20 carbon atoms, y is an integer from 1 to 8 and equals the valence of R R is a monovalent hydrocarbon radical selected from the group consisting of alkyl, aryl, alkaryl, and aralkyl of 1 to 40 carbon atoms and where X is selected from the group consisting of sulfur and oxygen.

2. A lubricant composition comprising di-2-ethylhexyl sebacate as the major component, and as minor components about 1 wt. percent phenothiazine and about 1 wt. percent triphenylurethane of trimethylolpropane.

3. A lubricant composition according to claim 1 also comprising between 0.2 and 1.5 wt. percent phenothiazine.

4. A lubricant composition according to claim 1 wherein said ester is di-Z-ethylhexyl sebacate, and said. polyurethane is triphenylurethane of trimethylolpropane.

5. A lubricant composition in accordance with claim 1 wherein said ester is di-Z-ethylhexyl sebacate, said polyurethane is the triphenylurethane of trimethylolpropane, and wherein said composition also includes between 0.2 and 1.5 wt. percent phenothiazine.

6. A lubricant composition according to claim 1 wherein said ester is di-Z-ethylhexyl sebacate, said polyurethane is triphenylthiourethane of trimethylolpropane wherein said composition also includes between 0.2 and 1.5 wt. percent phenothiazine.

7. A lubricant composition in accordance with claim 1 wherein said ester is di-Z-ethylhexyl sebacate, said polyurethane is diphenylurethane of 2,2-diethyl-l,3-propanediol and where said composition also includes between a 0.2 and 1.5 wt. percent of phenothiazine.

8. A lubricant composition according to claim 1 where in said ester is a tetraester of pentaerythritol and a mixture of C to C normal monobasic fatty acids, said polyurethane is the triphenylurethane of trimethylolpropane.

9. A lubricating composition according to claim 1 wherein said ester is a tetraester of pentaerythritol and a mixture of C to C normal monobasic fatty acids, said polyurethane is triphenylthiourethane of trimethylolproand wherein said composition also includes between 0.2 and 1.5 wt. percent phenothiazine.

10. A lubricating composition in accordance with claim 1 wherein said ester is a tetraester of pentaerythritol and a mixture of C to C normal monobasic fatty acids, said References Cited in the file of this patent UNITED STATES PATENTS 2,160,880 Loane ct a1 June 6, 1939 2,187,742 Johnson Jan. 23, 1940 2,781,319 Barnum et a1 Feb. 12, 1957 2,815,327 Mehr et a1 Dec. 3, 1957 OTHER REFERENCES Atkins et al.: Development of Additives and Lubricating Oil Compositions, I. and E. Chem. vol. 39, No. 4, April 1947, pp. 491-497.

Murphy et al.: Mode of Action of Phenothiazine Type Antioxidants, I. and E. Chem, vol. 42, No. 12, December 1950, p. 2479. 

1. A LUBRICANT COMPOSITION COMPRISING AS THE MAJOR COMPONENT AN ESTER FORMED FROM AN ACID SELECTED FROM THE GROUP CONSISTING OF SATURATED ALIPHATIC MONOCARBOXYLIC ACID AND SATURATED ALIPHATIC DICARBOXYLIC ACID OF 6 12 CARBON ATOMS AND A SATURATED ALIPHATIC ALCOHOL OF 6 TO 18 CARBON ATOMS CONTAINING 1 TO 4 HYDROXYL GROUPS AND AS A MINOR COMPONENT BETWEEN 0.1 TO 5.0 WT. PERCENT OF A URETHANE OF THE FORMULA 